Cool, I gave them a call, spoke to a nice lady... You have to buy minimum a case. On hand they had some synthetic Delvac 15w40 at 7.03$ plus tax per quart at 12 quarts per case. Then they had the synthetic 0w40 in 4L jugs at 4 jugs a case at 4.21$ per litre for 77.46 for a 16 litre case. I'd say that's pretty good..
Now, I'm running dino Valvoline 10w30, it was my first oil since the rebuild. These AMC engines are bad for rear main seal leakage, and I have a little leak right now. My experience has been that I never could run anything under dino 15w40 before for this reason. I tried semin synth 10w30 and it leaked before the rebuild. If what I understand is correct, the 0w40 would be my choice. The better cold crank ability with a weight that will keep the oil inside the seal..